A method in which the receiving sensitivity is adaptively adjusted as a function of the location of the useful sound source is described in German Patent No. 197 41 596. The sensitivity is controlled by evaluating audible signals received.
The method according to the present invention for controlling the sensitivity of at least one microphone has the advantage over the related art that video data of a sound source, in particular a speech source, is recorded by a camera, with the camera being located in a predetermined position relative to the at least one microphone; a position of the sound source relative to the at least one microphone is determined as a function of the recorded video data and/or a focus setting of a lens of the camera; and the sensitivity of the at least one microphone is adjusted as a function of the determined position. This makes it possible to adjust the sensitivity of the at least one microphone to the position of the sound source with an especially high degree of accuracy, requiring, in particular, no additional components if the camera is the camera of a videophone system and is therefore already provided. This increases the functionality of the camera. The at least one microphone can also be the microphone of the videophone system. During a video conference, the calling parties do not always find it easy to look directly into the camera while simultaneously speaking directly into the at least one microphone of the videophone system. For example, if the calling parties are working at a personal computer or perusing documents during the video conference, the actual direction in which they are speaking is often not in a direct line with the microphones. This means that incident noise from the environment is also transmitted. The method according to the present invention can be used to adjust the sensitivity of the at least one microphone to the actual speaking or sound direction once the latter has been determined by evaluating the video data and/or the focus setting of the lens, also making it possible to at least partially suppress the incident noise from the environment.
It is especially advantageous to adjust the sensitivity of the at least one microphone so that an audible signal emitted by the sound source at a first predetermined level in the direction of the at least one microphone is received by the at least one microphone at a second predetermined level. This ensures that, regardless of the distance between the sound source and the at least one microphone, the audible signals from the sound source are received at largely the same volume by the at least one microphone. For example, the volume thus remains largely constant when the speech is reproduced at a receiver of the videophone system regardless of the position in which the calling party, as the sound source, is located in front of the camera and regardless of the direction in which he is speaking.
A further advantage is the fact that the second predetermined level is set as a function of a reference position of the sound source relative to the at least one microphone. This makes it possible to adjust the sensitivity of the at least one microphone to the second predetermined level based on the reference position of the sound source, regardless of where the sound source is located, by determining the position of the sound source relative to its reference position and controlling the sensitivity accordingly.
One especially easy way to determine the position of the sound source relative to the at least one microphone is to determine a distance between the sound source and the at least one microphone as a function of the focus setting of the lens. This measure requires a minimum amount of effort.
The position of the sound source can be determined more precisely in that the position of the sound source is determined on the basis of the recorded video data by tracking at least one predetermined image segment of the sound source in consecutive images. Tracking only one image segment can save storage space for evaluating the video data, thus increasing the evaluation speed.
It is particularly advantageous to adjust a directional characteristic of the at least one microphone to the determined position of the sound source. This makes it possible to greatly suppress the reception of interference noise from the environment at the microphone.
It is particularly advantageous if audible signals from the sound source are received by two microphones; and, as the sound source moves in a way that reduces the distance from the sound source to a first microphone and increases the distance to a second microphone, the sensitivity of the second microphone is reduced and the sensitivity of the first microphone is adjusted so that an audible signal emitted by the sound source at the first predetermined level in the direction of the first microphone is received by the first microphone largely at the second predetermined level. This also makes it possible to greatly suppress interference noise from the environment when the audible signal is received by both microphones, since the different sensitivity settings of the two microphones also yield a directional characteristic that is adjusted to the determined position of the sound source. In addition, the audible signals are received by the microphones at a largely constant volume, regardless of the position of the sound source, so that the volume, in particular, remains largely constant when the speech is reproduced at the receiver of the videophone system.